The present invention relates to the actuation of a linear translatable member, such as an engine valve, and, more particularly, to actuation of a camless engine valve.
There is a need in the engine industry for greater control over the combustion process. The goal of such control is to provide for adequate power output while using fuel efficiently. In addition, unwanted emissions must be minimized, such emissions include: noxious by-products of the combustion process as well as noise. A reduction of noise emissions is particularly critical for compression ignition engines.
A way to achieve at least a portion of the control necessary to meet the afore-stated goals is by switching from cam operated engine valves to camless technology. Camless technology, at least in theory, allows direct control over dwell, the amount of valve opening (partial or full), the aggressiveness of the valve opening and closing, and other engine valve related parameters. Such control is highly advantageous in meeting the afore-mentioned goals.
Design of viable camless technology has not proven an easy task. One great concern in the viability of camless technology is the ability to control engine valve motion. Actuators that are coupled to the engine valve and that require substitution for typical cam engine valve lifts typically have required a sensor and a sophisticated feedback control system in order to control the engine valve motion. This results from the fact, that being directly coupled to the valve, requires such camless technology to account for valve lash arising from a variety of sources. Such systems have been experimented with by FEV, Siemens, Ford, Sturman, and others. Such systems demand large computer processors and the sheer size and cost of the control boards necessary for such processors have made them prohibitive both with respect to the space required proximate the engine valve, the cost of the processors themselves, and compromises to the design of internal combustion engines. The physical space proximate the engine valves for affecting engine valve motion is extremely limited, for this reason, the devices associated with camless technology need to be quite small as well as being reliable, fast, and accurate, while at the same time limiting the cost of such components.
The unit trigger actuator (UTA) of the present invention substantially meets the afore mentioned needs of the industry. The UTA relies on reducing the stroke of the actuator by a factor of between 2 and 3 while maintaining engine valve strokes comparable to cam actuation and prior art camless actuation. For these ratios, the reduced range of stroke of the UTA becomes much easier to control. Furthermore, the control may be affected without a sensor or feedback loop due to a unique means of lash control which decouples the UTA actuator from engine components. The advantage of open loop operation significantly decreases cost as well as increases reliability. Significantly, large tolerances in parts of assembly of the engine arrangement (length, variability from valve-to-valve, machining tolerances in the head in the upper and lower and firing decks, tolerance in the valve seats) become decoupled from the triggering action of the UTA. The internal parts of the UTA are decoupled from the engine parts through the play allowed in the lash adjustor. The lash adjustor further accounts for engine valve growth resulting from thermal effects.
The present invention is an actuator for actuating a linearly translatable member, such as an engine valve and includes a unit trigger actuator, the unit trigger actuator having a trigger being electrically actuatable, a hydraulic cartridge having a selectively translatable component and being operably coupled to the trigger for receiving actuation commands therefrom, the unit trigger actuator being an open loop system. A pivot element is operably coupled to the translatable component and to the engine valve, the pivot element amplifying motion imparted to the pivot element by translational motion of the piston at the engine valve. A lash adjuster is operably coupled to the pivot element for decoupling the hydraulic cartridge from lash inherent in a plurality of components and assembly of an engine valve arrangement. The present invention is further a method of actuation.